Hi, I've been playing with the beta firmware on my X-T1 together with my XF50-140mm at my daughter's soccer tournament this weekend. I also stumbled into a local MTB race when I was picking up my second daughter at a band camp yesterday and got to shoot some of the racers. I'm very impressed with this upgrade. AF-C and Zone focus are working great!
If anybody are interrested, I have written about my findings in this blogpost:
http://www.fujiboys.com/blog/2015/6/20/x-t1-firmware-40-afc-zone-wow
Tor Martin